When controlling an aircraft, a pilot must always recognize the conditions, which always changes, of a power system and a flight control system of an aircraft. Also, the pilot must know their operation limitations in addition to the current conditions of these systems.
A mechanical spring is sometimes used in an aircraft, and a sign (cue) through the tactile sense is given a pilot through a control lever to indicate the approach to an operation limitation of the aircraft. Such a mechanical spring supplies a given resistivity in the control in connection with a preset level. The preset level cannot be changed if the spring is once installed.
Patent Literature 1 (JP 2004-516970A) discloses an aircraft power lever tactile cueing system in which the magnitude of friction force can be changed according to a given dynamic condition of the aircraft, and in which the mechanical spring is not required. In this system, the mechanical spring is replaced by computer executed software, a variable magnetic particle friction clutch, and an electronic trim motor. A power lever soft stop and a power lever back drive are used as the tactile cautions. These tactile cautions provide the tactile cues in the same manner as the spring when the power command reaches a given operation limit. A back drive command trim-downs a power lever at a variable speed based on the operation situation of the aircraft and the engine. The tactile cue is set to an operation condition until the aircraft and the engine returns to a condition in which an operation limitation is not overrun.
On the other hand, FIG. 1 discloses a conventional flight control system using an inner loop command. The flight control system is provided with a flight control device 210, a control surface actuator 230, a swash plate 240, a control surface 250, an inner loop actuator 260, a rate gyro 270, and an inner loop command calculating section 280. The control surface actuator 230 is connected with the flight control device 210 through the inner loop actuator 260 and is connected with the control surface 250 through the swash plate 240. The control surface actuator 230 drives the control surface based on the flight control position of the flight control device 210. Here, the rate gyro 270 detects an attitude change of aircraft due to the disturbance and outputs the detected attitude change to the inner loop command calculating section 280. The inner loop command calculating section 280 outputs an inner loop command based on the detected posture change. The inner loop command is a command to increase or decrease a command amount which is given to the control surface actuator 230 without a change of the flight control position of the flight control device 210 by the pilot. The inner loop actuator 260 drives the control surface 250 through the control surface actuator 230 based on the inner loop command. Therefore, even if the flight control position of the flight control device 210 is maintained to be constant without fine correction by a pilot, it is prevented that the aircraft is made unstable due to the disturbance.